Refrigerating machine

ABSTRACT

A refrigerating machine is equipped with a compressor  1,  a radiator  2,  a pressure-reducing device  3,  a gas-liquid separator  4,  a unit for introducing the gas refrigerant separated in gas-liquid separator  4  into an intermediate pressure portion of the compressor, and a low pressure side circuit  9  in which liquid refrigerant separated in the gas-liquid separator is circulated. The low pressure side circuit  9  is provided with a heat absorbing unit  10  which selectively functions in different temperature zones. When the heat absorbing unit  10  is made to function in a high temperature zone, the gas refrigerant separated in the gas-liquid separator  4  is inhibited from being introduced into the intermediate pressure portion of the compressor  1  is inhibited, or allowed to be introduced into another intermediate pressure portion which is lower in pressure than the intermediate pressure portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigerating machine having arefrigerant introducing unit for selectively introducing gas refrigerantseparated in a gas-liquid separator into an intermediate pressureportion of a compressor.

2. Description of the Related Art

There is generally known a refrigerating machine equipped with acompressor, a radiator, a pressure-reducing device, a gas-liquidseparator and a refrigerant introducing unit for selectively introducinggas refrigerant separated in the gas-liquid separator into anintermediate pressure portion (JP-A-2003-106693). In this type ofrefrigerating machine, the gas refrigerant separated in the gas-liquidseparator is introduced into an intermediate pressure portion of thecompressor while keeping the refrigerant under gas state, so that theefficiency of the compressor can be enhanced.

This type of refrigerating machine is equipped with a heat absorbingunit containing a heat absorber which selectively functions in each ofdifferent temperature zones in a refrigerating cycle in some cases.

For example, when the refrigerating machine as described above isapplied to a refrigerator having a refrigerating chamber and a freezingchamber, a heat absorber functioning for refrigeration or freezing isdisposed in a refrigerating cycle, and a refrigerating or freezingoperation is carried out by using the function of any one heat absorber.In this case, it is important to carry out the operation with highefficiency without reducing the efficiency under any operation.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide arefrigerating machine in which when a heat absorbing unit selectivelyfunctioning in different temperature zones is provided in arefrigerating cycle, a high-efficiency operation can be performed in allthe temperature zones without reducing the efficiency.

In order to attain the above object, a refrigerating machine comprising:a compressor; a radiator; a pressure-reducing device; a gas-liquidseparator; a unit for introducing gas refrigerant separated in thegas-liquid separator into a first intermediate pressure portion of thecompressor; a low pressure side circuit in which liquid refrigerantseparated in the gas-liquid separator is circulated, the low pressureside circuit being equipped with an absorbing unit functioningselectively in different temperature zones; and a gas refrigerantintroduction inhibiting/allowing switching unit for inhibitingintroduction of the gas refrigerant separated in the gas-liquidseparator into the intermediate pressure portion of the compressor whenthe heat absorbing unit is made to function in a higher temperature zoneand allowing introduction of the gas refrigerant separated in thegas-liquid separator into a second intermediate pressure portion of thecompressor which is lower in pressure than the first intermediatepressure portion of the compressor.

In the above refrigerating machine, a part of the gas refrigerantintroduction inhibiting/allowing switching unit may be constructed by anopening/closing valve. Furthermore, another part of the gas refrigerantintroduction inhibiting/allowing switching unit may be constructed by athree-way valve and a branched gas pipe.

In the above refrigerating machine, the heat absorbing unit may beequipped with plural heat absorbers each of which functions selectivelyand is equipped with a unit for guiding cold air passed through the heatabsorber to a chamber which is controlled to the correspondingtemperature zone. The heat absorbing unit may be equipped with one heatabsorber which selectively functions in different temperature zones andis equipped with a unit for selectively guiding cold air passed throughthe heat absorber through a switching dumper to plural chambers whichare respectively controlled to different temperature zones. The heatabsorber may be disposed at a chamber which is controlled to a lowtemperature zone. In all the cases, refrigerant with which a highvoltage side is set to supercritical pressure under operation may befilled in a refrigerant circuit.

Furthermore, the three-way valve and the branch gas pipe may constitutegas refrigerant introducing unit which can introduce the gas refrigerantseparated in the gas-liquid separator to one of a first intermediatepressure portion of the compressor and a second intermediate pressureportion at a lower pressure suction side than the first intermediatepressure portion. When the heat absorbing unit is made to function in alow temperature zone, the gas refrigerant separated in the gas-liquidseparator is introduced to the first intermediate pressure portion ofthe compressor. On the other hand, when the heat absorbing unit is madeto function in a high temperature zone, the gas refrigerant isintroduced to the second intermediate pressure portion of thecompressor.

In this case, the heat absorbing unit may be provided with plural heatabsorbers which function in different temperature zones, and each of theheat absorbers may function selectively and may be equipped with a unitfor guiding cold air passed through the heat absorber concerned to achamber which is controlled to the corresponding temperature zone.Furthermore, each of the heat absorbers may be disposed in a chamberwhich is controlled to the corresponding temperature zone.

Furthermore, the heat absorbing unit may be provided with one heatabsorber which selectively functions in different temperature zones, andalso with a unit for selectively guiding cold air therefrom through aswitching dumper to plural chambers controlled to different temperaturezones. In this case, the heat absorber may be disposed in a chambercontrolled to a low temperature zone. In all the cases, carbon dioxiderefrigerant with which the high pressure side is set to supercriticalpressure under operation may be enclosed in the refrigerant circuit.

According to the present invention, the heat absorbing unit whichselectively functions in different temperature zones is provided to thelow pressure side circuit in which liquid refrigerant is circulated, andthe refrigerating machine is provided with the gas refrigerantintroduction inhibiting/allowing unit for inhibiting introduction of thegas refrigerant separated in the gas-liquid separator into theintermediate pressure portion of the compressor when the heat absorbingunit is made to function in a high temperature zone. Therefore, thehigh-efficient operation can be performed in the respective temperaturezones.

Furthermore, according to the present invention, the heat absorbing unitwhich selectively functions in different temperature zones is providedto the low pressure side circuit in which liquid refrigerant iscirculated, and the refrigerating machine is provided with the gasrefrigerant introducing unit for introducing the gas refrigerant intothe first intermediate pressure portion of the compressor when the heatabsorbing unit is made to function in a low temperature zone, andintroducing the gas refrigerant into the second intermediate pressureportion of the compressor when the heat absorbing unit is made tofunction in a high temperature zone. Therefore, the high-efficientoperation can be performed in the respective temperature zones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram showing a first embodiment of arefrigerating machine according to the present invention;

FIG. 2 is an enthalpy-pressure diagram of a refrigerating cycle;

FIG. 3 is a diagram showing an applied example to the first embodimentto a refrigerator;

FIG. 4 is a diagram showing an applied example to a refrigerator;

FIG. 5 is a refrigerant circuit diagram showing a modification of thefirst embodiment;

FIG. 6 is a diagram showing an applied example of the modification to arefrigerator;

FIG. 7 is a diagram showing an applied example to a refrigerator;

FIG. 8 is a refrigerant circuit diagram showing a second embodiment ofthe refrigerating machine according to the present invention;

FIG. 9 is an enthalpy-pressure diagram showing a refrigerating cycle;

FIG. 10 is a diagram showing an applied example of the second embodimentto a refrigerator, and corresponds to FIG. 3;

FIG. 11 is a diagram showing an applied example to a refrigerator andcorresponds to FIG. 4;

FIG. 12 is a refrigerant circuit diagram showing a modification of thesecond embodiment, and corresponds to FIG. 5;

FIG. 13 is a diagram showing an applied example to a refrigerator, andcorresponds to FIG. 6; and

FIG. 14 is a diagram showing an applied example to a refrigerator, andcorresponds to FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention will bedescribed hereunder with reference to the accompanying drawings.

FIG. 1 is a refrigerant circuit diagram showing a first embodimentaccording to the present invention. A refrigerating machine 30 isequipped with a compressor 1, a radiator 2, a first expansion valve(pressure-reducing device) 3 and a gas-liquid separator 4 which areconnected to one another in this order. A part of the refrigerantcircuit which extends from the compressor 1 through the radiator 2 tothe inlet port of the first expansion valve 3 constitutes ahigh-pressure side circuit.

The compressor 1 is a two-stage compressor, and it includes afirst-stage compressing portion 1A, a second-stage compressing portion1B and an intermediate cooler 1C between the first-stage andsecond-stage compressing portions 1A and 1B. Reference numeral 8represents a check valve. The refrigerating machine 30 is furtherequipped with a unit (gas refrigerant introduction inhibiting/allowingunit) 5 which selectively introducing gas refrigerant separated in thegas-liquid separator 4 into an intermediate pressure portion of thecompressor 1. In this construction, the intermediate pressure portion islocated between the intermediate cooler 1C and the second-statecompressing portion 1B. The compressor 1 of the present invention is notlimited to the two-stage compressor. If the compressor 1 is a one-stagecompressor, the gas refrigerant introduction inhibiting/allowing unit 5may be designed so as to return gas refrigerant to an intermediatepressure portion of the one-stage compressor. In this embodiment, thegas refrigerant introduction inhibiting/allowing unit 5 is constructedby a gas pipe 6 and an opening/closing valve 91 provided in the gas pipe6. Accordingly, the introduction of the gas refrigerant into theintermediate pressure portion is started (allowed) or stopped(inhibited) by opening/closing the opening/closing valve 91.

Furthermore, the refrigerating machine 30 is provided with alow-pressure side circuit 9 for circulating liquid refrigerant separatedin the gas-liquid separator 4, and the low-pressure side circuit 9 isprovided with a heat absorbing unit 10 which selectively functions indifferent temperature zones. The heat absorbing unit 10 is constructedby a second expansion valve 11 and one heat absorber 14. By controllingthe valve opening degree of the second expansion valve 11, theevaporating pressure in the heat absorber 14 is controlled. If theevaporating pressure is increased, the evaporating temperature isincreased, and thus a refrigerating operation is carried out. On theother hand, if the evaporating pressure is reduced, the evaporatingtemperature in the heat absorber 14 is lowered, and thus a freezingoperation is carried out. The refrigerant passed through the heatabsorber 14 is passed through the check valve 8 and returned to thesuction portion of the compressor 1.

In this embodiment, the heat absorber 14 is provided with a unit 23 forselectively guiding cold air passed through the heat absorber 14 toplural chambers (refrigerating chamber 21, freezing chamber 22) whichare controlled to different temperature zones. The unit 23 contains anair flowing duct 24 and a switching dumper 25, and a controller 26 forswitching the operation to one of the refrigerating and freezingoperations is connected to the switching dumper 25.

The controller 26 is also connected to the expansion valves 3 and 11 andthe opening/closing valve 91. For example when the load of the freezingchamber 22 is tilted, the switching dumper 25 is inclined to a positionindicated in FIG. 1 to guide cold air to the freezing chamber 22(freezing operation). Under freezing operation, the opening/closingvalve 91 is opened, and the gas refrigerant separated in the gas-liquidseparator 4 is introduced into the intermediate pressure portion of thecompressor 1 as indicated by a broken line. When the load of therefrigerating chamber 21 is increased, the switching dumper 25 is tiltedto the opposite position to the position shown in FIG. 1 to guide coldair to the refrigerating chamber 21 (refrigerating operation) Under therefrigerating operation, the opening/closing valve 91 is closed, and theintroduction of the gas refrigerant into the intermediate pressureportion of the compressor 1 is inhibited. The opening/closing valve 91constitutes the gas refrigerant introduction inhibiting/allowing unit.

The refrigerant circuit is filled with such refrigerant that thehigh-pressure side of the refrigerant circuit is set to supercriticalpressure under operation in accordance with a condition, for example,when the outside temperature is increased to 30° C. or more in summerseason, when the load is increased or the like. Carbon dioxiderefrigerant is filled as the above refrigerant. In place of carbondioxide refrigerant, ethylene, diborane, ethane, nitrogen oxide or thelike may be used as the refrigerant in which the high-pressure sidecircuit is operated under supercritical pressure.

In the above construction, even when the gas refrigerant separated inthe gas-liquid separator 4 is circulated in the low-pressure sidecircuit 9, it cannot be used for cooling. Accordingly, if the gasrefrigerant is turned to the suction port of the first-stage compressingportion 1A, it would reduce the efficiency of the refrigerating cycle.

Therefore, the gas refrigerant is introduced into the intermediatepressure portion of the compressor 1. In this embodiment, under thecontrol of the controller 26 described above, introduction of the gasrefrigerant into the intermediate pressure portion of the compressor 1is allowed under freezing operation in which the temperature zone islow. On the other hand, introduction of the gas refrigerant into theintermediate pressure portion is inhibited under refrigerating operationin which the temperature zone is high.

FIG. 2 is an enthalpy-pressure (ph) diagram showing a two-stagecompressor two-stage expansion cycle when gas refrigerant is introducedinto the first intermediate pressure portion X of the compressor 1 underboth the refrigerating operation and the freezing operation.

In FIG. 2, a cycle indicated by a solid line is formed during freezingoperation (freezing around −26° C.). (1) represents the suction port ofthe first-stage compressor 1A, (2) represents the discharge port of thefirst-compressing portion 1A, (3) represents the suction port of thesecond-stage pressing portion 1B, and (4) represents the discharge portof the second-stage compressing portion 1A. The refrigerant dischargedfrom the compressor 1 is circulated through the radiator 2 and cooled.(5) represents the inlet port of the first expansion valve 3, and (6)represents the outlet port of the first expansion valve 3. Under thestate of (6), the refrigerant becomes two-phase mixture of gas/liquid.

The ratio of gas and liquid corresponds to the ratio of the length ofthe line segment of L1 (gas) and the length of the line segment of L2(liquid). The refrigerant enters the gas-liquid separator 4 under thestate that the refrigerant keeps the two-phase mixture. The gasrefrigerant separated in the gas-liquid separator is introduced into theintermediate pressure portion of the compressor 1, that is, between theintermediate cooler 1C and the second-stage pressing portion 1B. (21)represents the outlet port of the gas-liquid separator 4. Therefrigerant passed through the outlet port of the gas-liquid separator 4reaches the suction port of the second-stage compressing portion 1B of(3), and then is compressed in the second-stage compressing portion 1B.The liquid refrigerant separated in the gas-liquid separator 4 iscirculated in the low-pressure side circuit 9. (7) represents the outletport of the gas-liquid separator 4, that is, the inlet port of thesecond expansion valve 11, (8) represents the outlet port of the secondexpansion valve 11 and (22) represents the outlet port of the heatabsorber 14. The liquid refrigerant entering the heat absorber 14evaporates to absorb heat. (1) represents the suction port of thefirst-stage compressing portion 1A.

On the other hand, a cycle indicated by a broken line is formed duringrefrigerating operation (refrigeration around −5° C.). That is, thestate of the cycle is varied in the following order: (9) the suctionport of the first-stage compressing portion 1A, (10) the discharge portof the first-stage compressing portion 1A, (11) the suction port of thesecond-stage compressing portion 1B, (12) the discharge port of thesecond-stage compressing portion 1B, (5) the inlet port of the firstexpansion valve 3, (13) the outlet port of the first expansion valve 3,(14) the outlet port of the gas-liquid separator 4 and thus the inletport of the second expansion valve 11, (15) the outlet port of thesecond expansion valve 11 and (9) the suction port of the first-stagecompressor 1A.

Referring to FIG. 2, the pressure (13) of the outlet port of the firstexpansion valve 3 in the broken-line cycle (under refrigeratingoperation) is remarkably higher than the pressure (6) of the outlet portof the first expansion valve 3 under the solid-line cycle (underfreezing operation). When the pressure of the outlet port of the firstexpansion valve 3 is increased, the amount of the gas component in therefrigerant before the refrigerant enters the gas-liquid separator 4 isreduced. This is because the ratio between gas and liquid at the inletport of the gas-liquid separator 4 corresponds to the ratio of L1 (gas)and L2 (liquid) or the ratio of L3 (gas) and L4 (liquid) as describedabove. In conformity with this, a large amount of gas refrigerant isintroduced into the intermediate pressure portion of the compressor 1under the solid-line cycle (freezing operation), however, the amount ofgas refrigerant to be introduced into the intermediate pressure portionis very small under the broken-line cycle (refrigerating operation).

That is, under freezing operation, the amount of the gas refrigerantintroduced into the intermediate pressure portion of the compressor 1 isincreased, and the efficiency of the refrigerating cycle can be enhancedby some degree because the gas component which does not contribute tocooling is not circulated in the low pressure circuit 9.

Particularly in the above construction, since carbon oxide refrigerantis filled in the refrigerant circuit, the amount of the gas component islarger as compared with chlorofluorocarbon (Freon) type refrigerant.Accordingly, a higher efficiency can be achieved by introducing a largeramount of gas component into the intermediate pressure portion of thecompressor 1. On the other hand, under refrigerating operation in whichthe temperature zone is high, the occurrence amount of gas refrigerantto be introduced into the intermediate pressure portion of thecompressor 1 itself is small, and thus even when the gas refrigerant isintroduced into the intermediate pressure portion, the efficiency of therefrigerating cycle cannot be so enhanced as compared with complicationin pipe construction, etc.

According to this embodiment, introduction of gas refrigerant into theintermediate pressure portion of the compressor 1 is allowed only underfreezing operation because of the effect of introducing the gasrefrigerant is higher. On the other hand, under refrigerating operationin which the temperature zone is high, introduction of gas refrigerantinto the intermediate pressure portion of the compressor 1 is inhibited.Therefore, the variable cycle can be implemented and the efficiency ofthe refrigerating cycle is enhanced by a simple pipe construction andsimple control.

Furthermore, according to this embodiment, all the parts of the heatabsorbing unit 10 which selectively function in different temperaturezones, that is, the second expansion valve 11 and the heat absorber 14are provided to the low pressure side circuit 9. Therefore, for examplewhen the refrigerating operation is carried out and when the freezingoperation is carried out, the remarkably highly efficient operation canbe performed without reducing the efficiency.

FIG. 3 shows an applied example of the refrigerating machine of theabove embodiment to a refrigerator.

A refrigerator (fridge) 40 has a refrigerating chamber 41 at the upperstage and a freezing chamber 42 at the lower stage. An inner partitionwall 43 is provided at the inner back side of the freezing chamber 42,and the heat absorber 14 described above is provided in an air flow path44 partitioned by the inner partition wall 43. A first switching dumper45 is disposed at the inlet port A of the air flow path 44, and thefirst switching dumper 45 is switched between a closing position(broken-line position) for closing the inlet port A of the air flow path44 and an opening position (solid-line position) for opening the inletport A of the air flow path 44. A back side air flow path 46 is formedon the back wall 47 of the refrigerator 40. When the first switchingdumper 45 is switched to the broken-line position, the inlet port 4 ofthe air flow path 44 and the refrigerating chamber 41 intercommunicatewith each other through the back side air flow path 46. Furthermore, afan 48 and a second switching dumper 49 are disposed at the outlet portB of the air flow path 44, and the second switching dumper 49 isswitched between a closing position (broken-line position) for closingthe outlet port B of the air flow path 44 and an opening position(solid-line position) for opening the outlet port B of the air flow path44. At the solid-line position, the second switching dumper 49 closes anopening 51 formed in an intermediate partition wall 50.

In the above construction, during freezing operation, the compressor 1is turned on, the fan 48 is turned on, the opening/closing valve 91 isopened, and each of the dumpers 45 and 49 is switched to the solid-lineposition. Accordingly, air in the freezing chamber 42 is circulated inthe heat absorber 14, and supplied to the freezing chamber 42. Duringrefrigerating operation, the opening/closing valve 91 is closed, andeach of the dumpers 45 and 49 is switched to the broken-line position.Accordingly, air in the refrigerating chamber 41 enters the air flowpath 44 through the back side air flow path 46, and it is circulated inthe heat absorber 14 and then supplied to the refrigerating chamber 41.

FIG. 5 shows a refrigerant circuit of a modification of the firstembodiment.

The construction of this modification is different from the constructionshown in FIG. 1 in the construction of the heat absorbing unit 10. Theheat absorbing unit 10 of this modification comprises a three-way valve11, a first capillary tube 12, a heat absorber 57 for refrigerationwhich is connected to the first capillary tube 12 in series, a secondcapillary tube 13 which is connected to the first capillary tube 12 andthe heat absorber 57, and a heat absorber 58 for freezing which isconnected to the second capillary tube 13 in series. Reference numeral59 represents a check valve. When the refrigerant is made to flow intothe first capillary tube 12 by switching the three-way valve 11, theflow amount of the refrigerant flowing in the heat absorber 57 isincreased, and the refrigerating operation is carried out. Furthermore,when the refrigerant is made to flow into the second capillary tube 13by switching the three-way valve 11, the flow amount of the refrigerantflowing in the heat absorber 58 is increased (the flow amount of therefrigerant flowing in the heat absorber 57 is reduced), and thus thefreezing operation is carried out.

FIG. 6 shows an applied example of the modification to a refrigerator(fridge).

The refrigerator 40 has a refrigerating chamber 41 at the upper stage,and a freezing chamber at the lower stage. Inner partition walls 61 and62 are provided at the inner back sides of the respective chambers 41and 42. The heat absorber 57, 58 and the fan 63, 64 are disposed in anair flow path 44 partitioned by the inner partition wall 61, 62. In thisconstruction, the three-way valve 11 is switched in accordance withthermo-on, thermo-off of the refrigerating operation and the freezingoperation to make the refrigerant flow into any one of the heatabsorbers 57 and 58, and the corresponding one of the fans 62 and 63 isdriven.

FIG. 7 shows another modification of the first embodiment.

This construction of this modification is different from theconstruction of FIG. 6 in the construction of the heat absorbing unit10. In the heat absorbing unit 10 of this modification, the three-wayvalve is omitted, and electrical motor operated valves 65 and 66 areconnected to the capillary tubes 12 and 13 in series, respectively. Inthis construction, the electrical motor operated valves 65 and 66 areturned on or off in accordance with thermo-on, thermo-off of therefrigerating operation and the freezing operation to make therefrigerant selectively flow into any one of the heat absorbers 57 and58, and the corresponding one of the fans 62 and 63 is driven. In theseembodiments, substantially the same effects can be achieved.

The present invention is not limited to the above embodiments, andvarious modifications may be made without departing from the subjectmatter of the present invention. In the above embodiments, the gasrefrigerant introduction inhibiting/allowing unit is constructed by theopening/closing valve 91, however, the present invention is not limitedto the opening/closing valve 91. For example, a circuit constructionachieved by combining a check valve, etc. may be used insofar as itintroduces the gas component of the refrigerant into the intermediatepressure portion of the compressor 1 under freezing operation while theintroduction of the gas component is inhibited under refrigeratingoperation.

Furthermore, in the above embodiments, carbon dioxide refrigerant isenclosed in the refrigerant circuit. However, the present invention isnot limited to carbon dioxide refrigerant, and it is needless to saythat chlorofluorocarbon (freon) type refrigerant or the like may beenclosed in the refrigerant circuit in place of carbon dioxiderefrigerant. Furthermore, the specific construction of the gasrefrigerant introducing unit 5 and the place from which the gascomponent is introduced are not limited to specific ones, and they maybe arbitrarily determined insofar as it can introduced the gas componentof the refrigerant into the intermediate pressure portion of thecompressor 1 in accordance with the operation condition.

In the above embodiments, the introduction of the gas refrigerant intothe intermediate pressure portion is inhibited on the assumption thatthe occurrence amount (L3) of the gas refrigerant introduced into theintermediate portion of the compressor 1 is small during refrigeratingoperation in which the temperature zone is high. However, when theoccurrence amount (L3) of the gas refrigerant is not small to the extentthat it cannot be neglected, the refrigeration efficiency can be furtherenhanced by designing the refrigerating machine so that the gasrefrigerant which does not contribute to cooling is prevented from beingcirculated in the low-pressure circuit side.

Next, an embodiment in which the gas refrigerant is introduced into thecompressor 1 under refrigerating operation to further enhance theefficiency of the refrigerating cycle.

FIG. 8 is a refrigerant circuit diagram showing a second embodiment ofthe present invention. A refrigerating machine 130 of this embodimenthas the same refrigerant circuit as the first embodiment except forapart of the construction. In the following description, the differentconstruction from the first embodiment will be mainly described. Thesame or corresponding constituent elements are represented by the samereferences, and the detailed description thereof is omitted.

The refrigerating machine 130 is equipped with a refrigerant gasintroducing unit 105 for selectively introducing gas refrigerantseparated in the gas-liquid separator 4 into one of a first intermediatepressure portion X of the compressor 1 and a second intermediatepressure portion Y which is nearer to the low pressure suction side thanthe first intermediate pressure portion X. In this construction, thefirst intermediate pressure portion X is located between theintermediate cooler 1C and the second-stage compressing portion 1B, andthe second intermediate pressure portion Y is located at some midpointof the first-stage compressing portion 1A. In this embodiment, thecompressor 1 comprises a two-stage compressor, however, the compressor 1is not limited to the two-stage compressor.

The gas refrigerant introducing unit 105 comprises a gas pipe 6, athree-way valve 81 provided in the gas pipe 6 and two branch gas pipes82 and 83 branched from the three-way valve 81. One branch gas pipe 82is connected to the first intermediate pressure portion X, and the otherbranch gas pipe 83 is connected to the second intermediate pressureportion Y. Here, the three-way valve 81 and the branch gas pipe 83constitutes the gas refrigerant introducing unit. Accordingly, when thegas pipe 6 and the branch gas pipe 82 intercommunicate with each otherby switching the three-way valve 81, the gas refrigerant is introducedinto the first intermediate pressure portion X as indicated by anbroken-line arrow. When the gas pipe 6 and the branch gas pipe 83intercommunicate with each other by switching the three-way valve 81,the gas refrigerant is introduced into the second intermediate pressureportion Y. Here, the three-way valve 81 is not limited to anelectromagnetic type, and a differential pressure driving type or thelike. Furthermore, the first intermediate pressure portion X correspondsto the intermediate pressure portion in the first embodiment.

The controller 26 is connected to the compressor 1, the expansion valves3 and 11 and the three-way valve 81. For example, when the load of thefreezing chamber 22 is increased, the valve opening degree of the secondexpansion valve 11 is increased, the flow amount flowing in the heatabsorber 14 is increased, and the switching dumper 25 is tilted to theposition shown in FIG. 8 to thereby guide cold air to the freezingchamber 22 (freezing operation). During freezing operation, thethree-way valve 81 is switched to make the gas pipe 6 and the branch gaspipe 82 intercommunicate with each other, so that the gas refrigerantseparated in the gas-liquid separator 4 is introduced into the firstintermediate pressure portion X as indicated by the broken-line arrow.Furthermore, when the load of the refrigerating chamber 21 is increased,the switching dumper 25 is tilted to the opposite position to theposition shown in FIG. 8 to guide cold air to the refrigerating chamber21 (refrigerating operation). During refrigerating operation, thethree-way valve 81 is switched to make the gas pipe 6 and the branch gaspipe 83 intercommunicate with each other, and the gas refrigerant isintroduced into the second intermediate pressure portion Y.

As in the case of the first embodiment, the refrigerant circuit isfilled with such refrigerant that the high-pressure side of therefrigerant circuit is set to supercritical pressure under operation inaccordance with a condition, for example, when the outside temperatureis increased to 30° C. or more in summer season, when the load isincreased or the like. Carbon dioxide refrigerant is filled as the aboverefrigerant. In place of carbon dioxide refrigerant, ethylene, diborane,ethane, nitrogen oxide or the like may be used as the refrigerant inwhich the high-pressure side circuit is operated under supercriticalpressure.

In the above construction, even when the gas refrigerant separated inthe gas-liquid separator 4 is circulated in the low pressure sidecircuit 9, it is not usable for cooling. Therefore, if the gasrefrigerant concerned is returned to the suction port of the first-stagecompressing portion 1A, the efficiency of the refrigerating cycle wouldbe reduced. Therefore, the gas refrigerant is introduced into theintermediate pressure portion of the compressor 1. However, as describedwith reference to the first embodiment, when the occurrence amount (L3)of the gas refrigerant is small, even if the gas refrigerant iscirculated in the low pressure side circuit 9, it hardly affects theefficiency of the refrigerating cycle. In other words, even when such asmall amount of gas refrigerant is introduced into the intermediatepressure portion of the compressor, it does not enhance the efficiencyof the refrigerating cycle. Accordingly, in this embodiment, under thecontrol of the controller 26 described above, the gas refrigerant isintroduced into the first intermediate pressure portion X of thecompressor 1 under freezing operation in which the temperature zone islow, and the gas refrigerant is introduced into the second intermediatepressure portion Y nearer to the low-pressure suction side of thecompressor 1 than the first intermediate pressure portion X underrefrigerating operation in which the temperature zone is high, wherebythe efficiency of the refrigerating cycle is further enhanced.

FIG. 9 is an enthalpy-pressure (ph) diagram showing the two-stagecompression two-stage expansion cycle when the gas refrigerant isintroduced into the first intermediate pressure portion X of thecompressor 1 under freezing operation in which the temperature zone islow while the gas refrigerant is introduced into the second intermediatepressure portion Y of the compressor 1 under refrigerating operation inwhich the temperature zone is high. Here, the ph diagram of FIG. 9 iscompared with the ph diagram of FIG. 2 when the gas refrigerant isintroduced into the first intermediate pressure portion X of thecompressor 1 in both the refrigerating and freezing operations.

In FIGS. 2 and 9, the refrigerating cycle indicated by a solid line isformed during freezing operation (freezing around −26° C.). (1)represents the suction port of the first-stage compressing portion 1A,(2) represents the discharge port of the first-stage compressing portion1A, (3) represents the suction port of the second-stage compressingportion 1B, and (4) represents the discharge port of the second-stagepressing portion 1B. The refrigerant discharged from the compressor 1 iscirculated through the radiator 2 to be cooled. (5) represents the inletport of the first expansion valve, and (6) represents the outlet port ofthe first expansion valve 3. Under this state, the refrigerant becomestwo-phase mixture of gas and liquid.

The ratio of gas and liquid corresponds to the ratio of the length ofthe line segment of L1 (gas) and the length of the line segment of L2(liquid). The refrigerant enters the gas-liquid separator 4 under thestate that the refrigerant is the two-phase mixture. The gas refrigerantseparated in the gas-liquid separator 4 is introduced into theintermediate portion of the compressor 1, that is, between theintermediate cooler 1C and the second-stage compressing portion 1B. (21)represents the outlet port of the gas-liquid separator 4. Therefrigerant passed through the gas-liquid separator 4 reaches the firstintermediate pressure portion X, that is, the suction port of thesecond-stage compressing portion 1B of (3), and compressed in thesecond-stage compressing portion 1B. On the other hand, the liquidrefrigerant separated in the gas-liquid separator 4 is circulated in thelow pressure side circuit 9. (7) represents the outlet port of thegas-liquid separator 4, and thus the inlet port of the second expansionvalve, (8) represents the outlet port of the second expansion valve 11,and (22) represents the outlet port of the heat absorber 14. The liquidrefrigerant entering the heat absorber 14 evaporates and absorbs heat.(1) represents the suction port of the first-stage compressing portion1A.

On the other hand, the cycle indicated by a broken line is formed underrefrigerating operation (refrigeration around −5° C.). That is, in FIG.9, the state is varied in the following order: (9) the suction port ofthe first-stage compressing portion 1A, (11) the second intermediatepressure portion Y, that is, the intermediate portion of the first-stagepressure compressing portion 1A, (12) the discharge port of thefirst-stage compressing portion 1A and thus the inlet port of theintermediate cooler 1C, (13) the outlet port of the intermediate cooler1C and thus the suction port of the second-stage compressing portion 1B,(14) the discharge port of the second-stage compressing portion 1B, (5)the inlet port of the first expansion valve 3, (15) the outlet port ofthe first expansion valve, (16) the outlet port of the gas-liquidseparator 4 and thus the inlet port of the second expansion valve 11,(17) the outlet port of the second expansion valve 11, and (9) thesuction port of the first-stage compressing portion 1A.

In FIG. 2, the gas refrigerant is introduced into the first intermediatepressure portion X of the compressor 1, and thus the state is varied inthe following order: (9) the suction port of the first-stage compressingportion 1A, (10) the discharge port of the first-stage compressingportion 1A, (11) the first intermediate pressure portion X, that is, theoutlet port of the intermediate cooler 1C, and thus the suction port ofthe second-stage compressing portion 1B, (12) the discharge port of thesecond-stage compressing portion 1B, (5) the inlet port of the firstexpansion valve 3, (13) the outlet port of the first expansion valve 3,(14) the outlet port of the gas-liquid separator 4, that is, the inletport of the second expansion valve 11, (15) the outlet port of thesecond expansion valve 11 and the suction port of the first-stagecompressing portion 1A.

When comparing the cases of FIGS. 2 and 9, the gas refrigerant isintroduced into the first intermediate pressure portion X of thecompressor 1 under freezing operation in which the temperature zone islow in both the cases. Accordingly, under freezing operation,substantially the same cycle indicated by the solid line is formed inFIGS. 2 and 9.

On the other hand, under the refrigerating operation in which thetemperature zone is high, the gas refrigerant is introduced into thesecond intermediate pressure portion Y nearer to the low voltage suctionside than the first intermediate pressure portion X in FIG. 9 whereasthe gas refrigerant is introduced into the first intermediate pressureportion X of the compressor 1 in FIG. 2. The pressure of the secondintermediate pressure portion Y is lower than the pressure of the firstintermediate pressure portion X. Accordingly, when the gas refrigerantis introduced into the second intermediate pressure portion Y having thelower pressure, the pressure at the outlet port of the first expansionvalve 3 can be reduced as compared with the case where the gasrefrigerant is introduced into the first intermediate pressure portionX.

That is, under refrigerating operation, the pressure of the linesegments L5 and L6 (FIG. 9) is lower than the pressure of the linesegments L3 and L4 (FIG. 2) in the cycle indicated by the broken line.When the pressure at the outlet port of the first expansion valve 3 isreduced, the amount of the gas component of the refrigerant before itenters the gas-liquid separator 4 is increased. This is also apparentfrom the fact that the line segment L5 is longer than the line segmentL3. As described above, the ratio of gas and liquid at the inlet port ofthe gas-liquid separator 4 corresponds to the ratio of L5 (gas) and L6(liquid) in FIG. 9, and also corresponds to the ratio of L3 (gas) and L4(liquid) in FIG. 2. Accordingly, the amount of the gas refrigerantintroduced into the intermediate pressure portion of the compressor 1 islarger as compared with FIG. 2, and thus it cannot be neglected.Therefore, the efficiency of the refrigerating cycle can be enhanced bythe degree corresponding to the effect achieved when the gas componentwhich does not contribute to cooling is prevented from being circulatedin the low pressure circuit 9. Particularly, in the above construction,carbon dioxide refrigerant is enclosed in the refrigerant circuit, andthus the amount of the gas component of the refrigerant is larger in theratio of gas and liquid separated in the gas-liquid separator 4 ascompared with chlorofluorocarbon (Freon) type refrigerant, and a largeramount of gas component is introduced to the intermediate pressureportion o the compressor 1, whereby the efficiency of the refrigeratingcycle can be more enhanced.

In this embodiment, all the elements of the heat absorbing unit 10 whichselectively functions in different temperature zones, that is, thesecond expansion valve 11 and the heat absorber 14 are provided to thelow pressure side circuit 9. Therefore, in both the case where therefrigerating operation is carried out and the case where the freezingoperation is carried out, the highly efficient operation can beperformed without reducing the efficiency.

The refrigerating machine may be designed so that the gas refrigerantintroduction inhibiting/allowing unit 5 according to the firstembodiment and the gas refrigerant introducing unit 105 according to thesecond embodiment is connected to each other in series. In this case,both the units are switched to each other in accordance with thereduction of the efficiency of the refrigerating cycle which is causedby the occurrence amount of the gas refrigerant under refrigeratingoperation. Specifically, the gas refrigerant introductioninhibiting/allowing unit 5 is secured to the gas refrigerant dischargeside of the gas-liquid separator 4, and the gas refrigerant introducingunit 105 is secured to the output side of the gas refrigerantintroduction inhibiting/allowing unit 5.

The gas refrigerant introducing unit 105 may be designed so as tointroduce the refrigerant into the first intermediate pressure portionof the compressor 1 or the second intermediate pressure portion nearerto the suction side of the compressor 1 than the first intermediatepressure portion in accordance with the operating condition, and thespecific construction thereof and the introducing position thereof aredetermined freely.

FIGS. 10 to 14 show examples when the above embodiment is applied to arefrigerator, and correspond to FIGS. 3 to 7 when the gas refrigerantintroduction inhibiting/allowing unit 5 is changed to the gas.refrigerant introducing unit 105. Each operation in the refrigerator isidentical to the corresponding operation described with reference toFIGS. 3 to 7, and the duplicative description thereof is omitted.

As described above, according to the present invention, under freezingoperation having a higher effect, the gas refrigerant is introduced intothe intermediate pressure portion (first intermediate pressure portion)of the compressor 1, and under refrigerating operation in which thetemperature zone is high, the gas refrigerant is introduced into theintermediate pressure portion (second intermediate pressure portion) atthe lower pressure side than the first intermediate pressure portion.Therefore, the variable cycle can be implemented and the efficiency ofthe refrigerating cycle can be enhanced by a simple pipe constructionand a simple control operation.

The gas refrigerant introducing inhibiting/allowing unit of the firstembodiment and the gas refrigerant introducing unit of the secondembodiment may be used independently of each other, however, acombination thereof may be arranged a gas refrigerant introductioninhibiting/allowing switching unit having both the functions thereof inthe gas pipe 6 between the gas-liquid separator 4 and the compressor 1.In this case, the gas refrigerant introduction inhibiting/allowing unit5 is provided at the gas-liquid separator 4 side while the gasrefrigerant introducing unit 105 is disposed between the gas refrigerantintroduction inhibiting/allowing unit 5 and the compressor 1.Furthermore, under freezing operation, the gas refrigerant introductioninhibiting/allowing unit and the gas refrigerant introducing unit areoperated so that the gas refrigerant from the gas-liquid separator 4 ispassed through the gas refrigerant introduction inhibiting/allowingunit, and further passed through the gas refrigerant introducing unit tothe first intermediate pressure portion X of the compressor 1. On theother hand, under refrigerating operation, the gas refrigerantintroduction inhibiting/allowing unit and the gas refrigerantintroducing unit are selectively operated so that the gas refrigerantfrom the gas-liquid separator 4 is inhibited from being introduced tothe compressor by the gas refrigerant introduction inhibiting/allowingunit or allowed to be introduced to the compressor through the gasrefrigerant introduction inhibiting/allowing unit, passed through thegas refrigerant introducing unit and then introduced to the secondintermediate pressure portion Y of the compressor in accordance with thecondition such as the gas refrigerant amount at the outlet port of thefirst expansion valve 3 or the like.

The present invention is not limited to the above embodiments, andvarious modifications may be made without departing from the subjectmatter of the present invention. For example, in the above construction,carbon dioxide refrigerant is enclosed in the refrigerant circuit,however, the present invention is not limited to carbon dioxiderefrigerant. For example, chlorofluorocarbon (Freon) type refrigerant orthe like may be enclosed in the refrigerant circuit in place of carbondioxide refrigerant.

1. A refrigerating machine comprising: a compressor; a radiator; apressure-reducing device; a gas-liquid separator; a unit for introducinggas refrigerant separated in the gas-liquid separator into a firstintermediate pressure portion of the compressor; a low pressure sidecircuit in which liquid refrigerant separated in the gas-liquidseparator is circulated, the low pressure side circuit being equippedwith an absorbing unit functioning selectively in different temperaturezones; and a gas refrigerant introduction inhibiting/allowing unit forinhibiting introduction of the gas refrigerant separated in thegas-liquid separator into the intermediate pressure portion of thecompressor when the heat absorbing unit is made to function in the hightemperature zone.
 2. The refrigerating machine according to claim 1,wherein the gas refrigerant introduction inhibiting/allowing unit isconstructed by an opening/closing valve.
 3. The refrigerating machineaccording to claim 1, wherein the heat absorbing unit is equipped withplural heat absorbers each of which functions selectively and isequipped with a unit for guiding cold air passed therethrough to achamber controlled to the corresponding temperature zone.
 4. Therefrigerating machine according to claim 3, wherein each of the heatabsorbers is disposed in a chamber controlled to the correspondingtemperature zone.
 5. The refrigerating machine according to claim 1,wherein the heat absorbing unit is equipped with one heat absorber whichselectively functions in different temperature zones and is equippedwith a unit for selectively guiding cold air passed therefrom through aswitching dumper to plural chambers which are respectively controlled todifferent temperature zones.
 6. The refrigerating machine according toclaim 5, wherein the heat absorber is disposed at a chamber controlledto a low temperature zone.
 7. The refrigerating machine according toclaim 1, wherein refrigerant with which a high voltage side is set tosupercritical pressure under operation is enclosed in a refrigerantcircuit.
 8. A refrigerating machine comprising: a compressor; aradiator; a pressure-reducing device; a gas-liquid separator; a unit forintroducing gas refrigerant separated in the gas-liquid separator into afirst intermediate pressure portion of the compressor; a low pressureside circuit in which liquid refrigerant separated in the gas-liquidseparator is circulated, the low pressure side circuit being equippedwith an absorbing unit functioning selectively in different temperaturezones; and a gas refrigerant introducing unit for selectivelyintroducing the gas refrigerant separated in the gas-liquid separatorinto one of the first intermediate pressure portion of the compressorany a second intermediate pressure portion nearer to a low pressuresuction port of the compressor than the first intermediate pressureportion, wherein the gas refrigerant introducing unit introduces the gasrefrigerant separated in the gas-liquid separator into the firstintermediate pressure portion when the heat absorbing unit is made tofunction in a low temperature zone, and introduces the gas refrigerantseparated in the gas-liquid separator into the second intermediatepressure portion of the compressor when the heat absorbing unit is madeto function in a high temperature zone.
 9. The refrigerating machineaccording to claim 8, wherein the heat absorbing unit is equipped withplural heat absorbers each of which functions selectively and isequipped with a unit for guiding cold air passed therethrough to achamber controlled to the corresponding temperature zone.
 10. Therefrigerating machine according to claim 9, wherein each of the heatabsorbers is disposed in a chamber controlled to the correspondingtemperature zone.
 11. The refrigerating machine according to claim 8,wherein the heat absorbing unit is equipped with one heat absorber whichselectively functions in different temperature zones and is equippedwith a unit for selectively guiding cold air passed therefrom through aswitching dumper to plural chambers which are respectively controlled todifferent temperature zones.
 12. The refrigerating machine according toclaim 11, wherein the heat absorber is disposed at a chamber controlledto a low temperature zone.
 13. The refrigerating machine according toclaim 8, wherein refrigerant with which a high voltage side is set tosupercritical pressure under operation is enclosed in a refrigerantcircuit.